A variety of information can be made available to users on a network, such as the Internet. Content stored by various content hosts can be obtained from a variety of sources, including users of the content hosts. Several applications provide a user with features that allow the user to add content to the hosts. For example, web site publishers include text editors in web pages to allow a user to add text resources and to upload the added resources to one or more content hosts. In this manner, resources can be collected from several users. Search engines, e.g., the Google™ search engine offered by Google Inc. (Mountain View, Calif.) enable a user to search for resources on the network. Users generally interact with search engines through web sites, such as www.google.com, where a user can enter a search query.
Search engine can search a searchable index generated from a corpus of resources on the network and identify resources that are responsive to the search query. Indexing the resources in the corpus allows for efficient searching.